The Screening And Inhibitory Effects Of Antagonistic Bacteria Of The Stone Fruit Post-harvest Diseases

The postharvest diseases happened seriously in stone fruits, the decay rate couldbe up to50%and caused huge economic losses, became an important factor whichrestricted the production. The pathogens which caused the peach [Prunuspersica(L.)Batsch cv. bai feng] and apricot [Armeniara vulgaris Lam. cv. Dajiexing]decay were isolated in this study. And the effective antagonistic strains were screenedto inhibit postharvest pathogens. The classification, identification and inhibitoryeffects of the antagonistic bacteria were studied preliminarily so as to providetheoretical basis for the biological control of postharvest diseases of stone fruits. Themain findings were as follows:1. Six major pathogens were isolated from different storage periods, according tothe disease symptoms of infected fruit, characteristics of pathogens colony and themycelial morphology. These six major pathogens were identificated as Alternariaalternate, Botrytis cinerea, Rhizopus nigricans, Penicillium frequentans,Trichothecium roseum and Aspergillus niger respectively. The isolation frequency ofAlternaria alternata and Botrytis cinerea were higher than other pathogens, followedby39.66%and31.88%, were the main pathogens causing postharvest diseases; theisolation frequency of Rhizopus nigricans, Penicillium frequentans, Trichotheciumroseum and Aspergillus niger were slightly lower, followed by18.21%,5.96%,3.41%and0.89%respectively, but also have pathogenicity on fruits.2. There were14strains which had inhibition effect on these six kinds ofpathogens, accounting for13.46%of the total number of isolation by the methods ofplant tissue isolation, fruit surface isolation and soil dilution isolation respectively.The results of in vitro and in vivo screening showed that: the antagonistic role ofstrains JK-14and JK-11were the most significant; the inhibitory effect R forAlternaria alternate and Botrytis cinerea were0.74and0.68,0.74and0.73respectively; these two antagonistic strains could obviously inhibited the growth ofpathogens hypha; the incidence and the disease spot diameter of the treatment fruits were significantly less than the control. By the methods of morphological,physiological and biochemical, molecular biological to identify, JK-14had highhomology with multiple strains of Bacillus sp. in16S rDNA sequences; JK-11werehomologous higher with multiple strains of Paenibacillus sp.. Through geneticclustering analysis, JK-14were Bacillus sp. and JK-11were Paenibacillus sp..3. The inhibitory effect measurement results of antagonistic bacteria showed thatthe fermentation broth, bacterial suspension and culture filtrate of strains JK-14,JK-11had different levels of inhibitory effect on postharvest pathogens. Theincidence and the disease spot diameter of the treatment fruits were significantly lessthan the control. The different concentrations of fermentation broth and bacterialsuspension showed that the best concentration of inhibitory effect was107CFU/mL,the difference with other concentrations was significantly. The results of fermentationtime treatment showed that the incidence and the disease spot diameter were the leastwith the38h antagonistic broth treated. The induced resistance for the host showedthat antagonistic bacteria and their secreted metabolites could promote the activity ofSOD and POD in fruits, reduced the content of MDA effectively caused by pathogenseffectively; thereby the disease resistance of the fruit itself could be improved.4.The study of strains JK-14, JK-11combined with fruit wax on fruit qualityshowed that the natural decay rate of treatment peach fruit were lower than the watercontrol; the inhibitory treatment effect of bacterial suspension was the best;fermentation broth followed; the effect of fruit wax combined with the antagonisticstrains was not as good as the effect of using them alone, and the fermentation filtratewas the worst treatment. The measurement results on the weight loss rate of fruit,hardness, soluble solids, conductivity, titratable acidity and vitamin C content showedthat the antagonistic bacteria of different treatment could delay the hardness decreases,the increase of cell membrane permeability, reduced titratable acid and Vc content ofstorage period, delayed the deterioration of fruit quality during storage periods.